Fix hashmap class, remove comments, interface implmemented, use a better hash function

Author: Hugo Venega

.eslintrc.js

@@ -13,5 +13,7 @@ module.exports = {
     project: './tsconfig.json'
    },
   plugins: ['@typescript-eslint'],
-  rules: {},
+  rules: {
+    'class-methods-use-this': 'off',
+  },
 };

src/hashmap/hashmap.spec.ts

@@ -15,7 +15,7 @@ describe('HashMaP', () => {
   });
   it('should return the requested item', () => {
     hashmap.set('pepe', { n: 12 });
-    expect(hashmap.get('pepe')).toEqual(['pepe', { n: 12 }]);
+    expect(hashmap.get('pepe')).toEqual({ key: 'pepe', value: { n: 12 } });
   });
   it('should return undefined when the key not hashed', () => {
     expect(hashmap.get('zapallo')).toEqual(undefined);

src/hashmap/hashmap.ts

@@ -1,39 +1,51 @@
 import BinarySearchTree from '../tree/BST/binarySearchTree';
 
-const ARRAY_SIZE = 10;
+interface HashMapElement<T>{
+  key: string,
+  value?: T
+}
+
+const ARRAY_SIZE = 1000;
 
-export default class HashMap<T> {
-  private memory : BinarySearchTree<[string, T | null]>[] = [];
+export default class HashMap<T = any> {
+  private memory : BinarySearchTree<HashMapElement<any>>[] = [];
 
   public length = 0;
 
-  private compareFunction = (a:[string, T | null],
-    b:[string, T | null]): number => a[0].localeCompare(b[0]);
+  private compareFunction = (a: { key: string },
+    b:HashMapElement<any>): number => a.key.localeCompare(b.key);
 
   set(key: string, value: T): void {
     const placeToAdd = this.hashFunction(key) % ARRAY_SIZE;
     if (!this.memory[placeToAdd]) {
-      this.memory[placeToAdd] = new BinarySearchTree<[string, T | null ]>(this.compareFunction);
+      this.memory[placeToAdd] = new BinarySearchTree<HashMapElement<any>>(this.compareFunction);
     }
-    this.memory[placeToAdd].add([key, value]);
+    this.memory[placeToAdd].add({ key, value });
     this.length += 1;
   }
 
-  get(key: string): [string, T | null ] | undefined {
+  get(key: string): HashMapElement<any> | undefined {
     const positionInArray = this.hashFunction(key) % ARRAY_SIZE;
     const treeInArray = this.memory[positionInArray];
     if (!treeInArray) {
       return undefined;
     }
-    const result = treeInArray.search([key, null]);
+    const result = treeInArray.search({ key });
     if (!result) {
       return undefined;
     }
     return result;
   }
 
-  // eslint-disable-next-line class-methods-use-this
-  private hashFunction(key:string): number {
-    return key.length;
+  private hashFunction(key: string): number {
+    let hashValue = 0;
+    const stringKey = key.toString();
+
+    for (let index = 0; index < stringKey.length; index += 1) {
+      const charCode = stringKey.charCodeAt(index);
+      hashValue += charCode;
+    }
+
+    return hashValue;
   }
 }